1. Field of the Invention
The present invention relates to an extendable/contractible strap device which is usable for a mobile-phone or a bag.
2. Background of the Invention
A bag, to which a shoulder strap (shoulder belt) is attached, is convenient, for example, when the load of a bag is heavy or when the hands of a user are intended to be made free, because the bag can be retained by hanging the shoulder strap on the shoulder. However, when the shoulder strap is not used, the shoulder strap hangs down from the main body of the bag, which gives an unseemly appearance. Further, there some problems in which the shoulder strap hanging down from the main body of the bag may be caught by any object or obstacle, possibly resulting in an accident in some cases and in which the shoulder strap contacts with the floor, which is unfavorable in view of hygiene.
Japanese Patent No. 3359627 corresponding to U.S. Pat. No. 6,669,068 to the present inventor discloses an extendable/contractible strap which is provided with two sliders (guides) movable on straps. This strap was innovative because the strap device can extend to three or four times of original length on demand. However, because one slider is located in the middle of the strap when it is extended, it needs to prevent from interfering the slider with user's body. Further, when it is accommodated (contracted), an inconvenient operation using both hands is necessary to part the two sliders from each other.
Various types of straps are used for mobile-phones or key rings. Because ordinary ring-like straps do not change in length, they are not convenient although it has a clip on the end of the strap. A coil-like strap which is extendable is commercially available, but it cannot support a phone when a portion of the coil-like strap is held, like the ring-like strap. Thus, there might be a demand for a strap which can be easily handled and is extendable.